The overall purpose of this research is to determine the essentiality of lithium as a nutrient; specifically, the research will examine the effects of physiological levels of dietary lithium on the levels of various neurotransmitters (acetylcholine, serotonin, norepinephrine, and dopamine) in brain, the lithium concentrative effect of various endocrine glands, and the effect of low dietary lithium on reproduction. Two groups of albino rats will be used in this study. A low-lithium group will be fed a diet maintained at a lithium level of 0.010 ppm or less; an adequate-lithium group will be fed a diet supplemented with 0.5 ppm lithium. Animals from each diet group will be carried through three generations to assess reproductive performance. A subsample of the animals from each diet group within each generation will be sacrificed and various endocrine and non-endocrine tissues removed. Lithium content of the tissues will be determined by flame emission, and neurotransmitter concentrations in the brain will be determined. Through this procedure we should be able to determine which tissues tend to concentrate lithium (in order to gain a more complete understanding of the physiological role of lithium), and show whether or not physiological levels of lithium influence the levels of important neurotransmitters in the brain.